Steerable catheter with distal tip orientation sheaths

ABSTRACT

A bi-directional electrophysiology catheter having improved steerability which includes orientation sheaths, or thin walled tubes, placed in diametrically opposed lumen at the distal portion of the catheter for producing in-plane deflection of the distal portion of the catheter.

FIELD OF THE INVENTION

The present invention relates to an improved steerable electrophysiologycatheter having a mechanism in the distal tip of the catheter to orientdeflection.

BACKGROUND OF THE INVENTION

Electrophysiology catheters have been in common use in medical practicefor many years. Such catheters are used to stimulate and map electricalactivity in the heart and to ablate sites of aberrant electricalactivity.

In use, the electrophysiology catheter is inserted into a major vein orartery, e.g., femoral artery, and then guided into the chamber of theheart which is of concern. Within the heart, the ability to control theexact position and orientation of the catheter tip is critical andlargely determines how useful the catheter is.

Steerable (or deflectable) electrophysiology catheters are generallywell known. For example, U.S. Pat. No. Re. 34,502 describes a catheterhaving a control handle comprising a housing having a piston chamber atits distal end. A piston is mounted in the piston chamber and isafforded lengthwise movement. The proximal end of the catheter body isattached to the piston. A puller wire is attached to the housing andextends through the piston and through the catheter body. The distal endof the puller wire is anchored in the tip section of the catheter. Inthis arrangement, lengthwise movement of the piston relative to thehousing results in deflection of the catheter tip section.

Often it is desirable to have a bidirectional steerable catheter, i.e.,a catheter that can be deflected in two directions, typically opposingdirections. For example, U.S. Pat. No. 6,210,407 discloses abidirectional steerable catheter having two puller wires extendingthrough the catheter. The distal ends of the puller wires are anchoredto opposite sides of the tip section of the catheter. A suitablebidirectional control handle is provided that permits longitudinalmovement of each puller wire to thereby allow deflection of the catheterin two opposing directions.

Regardless of whether the catheter is unidirectional or bidirectional,it is typically preferred that the tip section can be deflected in theplane of the catheter so that the catheter can be more preciselycontrolled in the heart. However, because the tip section is generallymade of a flexible material, it is sometimes difficult to limitout-of-plane deflection. Accordingly, a need exists for a catheterhaving a tip section that can be consistently deflected within a singleplane of the catheter.

SUMMARY OF THE INVENTION

The present invention is directed to an improved electrophysiologysteerable catheter having orientation sheaths, or tubes, extendingthrough the distal end to improve deflection. More particularly, thecatheter includes an elongated, flexible tubular catheter body havingproximal and distal ends and a lumen extending therethrough. A tipsection is provided at the distal end of the catheter body. The tipsection includes flexible plastic tubing having first and second pairsof diametrically opposed lumens extending therethrough. The first pairof diametrically opposed lumens are generally perpendicular to thesecond pair of diametrically opposed lumens. A control handle is mountedat the proximal end of the catheter body. The catheter further includesfirst and second puller wires, each extending through one of the lumensof the first pair of diametrically opposed lumens and through the lumenof the catheter body. The puller wires each have a proximal end anchoredto the control handle and a distal end anchored to the tip section. Thefirst puller wire is longitudinally moveable relative to the catheterbody to cause deflection of the tip section in a plane in a firstdirection, and the second puller wire is longitudinally moveablerelative to the catheter body to cause deflection of the tip section ina plane in a second direction opposite the first direction. The catheterfurther comprises first and second orientation sheaths, or tubes, eachhaving proximal and distal ends. Each orientation sheath extends throughone of the lumens of the second pair of diametrically opposed lumens.The distal end of each orientation sheath is fixedly attached to thewall of the respective lumen at or near the distal end of the tipsection, and the proximal end of each orientation sheath is fixedlyattached to the wall of the respective lumen at a more proximal portionof the respective lumen.

DESCRIPTION OF THE DRAWINGS

These and other features of the advantages of the present invention willbe better understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a side view of an embodiment of the catheter of the invention.

FIG. 2 is a side cross-sectional view of the junction of the catheterbody and tip section of an embodiment of a catheter according to theinvention.

FIG. 3 is a transverse cross-sectional view of the catheter body shownin FIG. 2 taken along line 3-3.

FIG. 4 is a side cross-sectional view of the tip section of the catheterof the invention showing the lumens through which the orientationsheaths and electrode lead wires extend.

FIG. 5 is a side cross-sectional view of the tip section of the catheterof the invention showing the lumens through which the pullers extend.

FIG. 6 is an end cross-sectional view of the tip section rotated 90degrees from the view shown in FIG. 5.

FIG. 7 is an end cross-sectional view of the tip section of FIGS. 4 and6 taken along liens 7-7.

DETAILED DESCRIPTION

In a particularly preferred embodiment of the invention, there isprovided a steerable bidirectional electrode catheter. As shown in FIG.1, the catheter 10 comprises an elongated catheter body 12 havingproximal and distal ends, a tip section 14 at the distal end of thecatheter body 12, and a control handle 16 at the proximal end of thecatheter body 12.

As shown in FIGS. 2 and 3, the catheter body 12 comprises an elongatedtubular construction having a single axial or central lumen 18. Thecatheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. A presentlypreferred construction comprises an outer wall 20 made of polyurethaneor PEBAX. The outer wall 20 preferably comprises an imbedded braidedmesh of stainless steel or the like to increase torsional stiffness ofthe catheter body 12 so that when the control handle 16 is rotated thetip section 14 will rotate in a corresponding manner.

The overall length and diameter of the catheter 10 may vary according tothe application. A presently preferred catheter 10 has an overall lengthof about 48 inches. The outer diameter of the catheter body 12 is notcritical, but is preferably no more than about 8 french. The innersurface of the outer wall 20 is preferably lined with a stiffening tube22, which can be made of any suitable material, preferably nylon orpolyimide. The stiffening tube 22, along with the braided outer wall 20,provides improved flexural and torsional stability while at the sametime minimizing the wall thickness of the catheter body 12, thusmaximizing the diameter of the central lumen 18. The outer diameter ofthe stiffening tube 22 is about the same as or slightly smaller than theinner diameter of the outer wall 20. A particularly preferred catheter10 has an outer diameter of about 0.092 inch and a lumen 18 diameter ofabout 0.052 inch. If desired, the stiffening tube can be omitted.

As shown in FIGS. 4, 5 and 6, the tip section 14 comprises a shortsection of flexible tubing 19 having four off-axis lumens 23, 24, 25 and26 extending therethrough. The flexible tubing 19 can comprise a singleunitary piece of plastic or can comprise a series of layers, as isgenerally known in the art. For example, the flexible tubing 19 cancomprise a plastic core, an inner plastic layer surrounding the core, abraided stainless steel mesh surrounding the inner layer, and an outerplastic layer surrounding the braided mesh. The core is preferably madeby extruding the plastic over four mandrels to thereby form the fouroff-axis lumens 23, 24, 25 and 26, where the mandrels are removed afterthe core is extruded. The inner layer is formed over the core by anysuitable technique, such as extrusion, which can be performedsimultaneously with the extrusion of the core. Thereafter, the braidedmesh is formed over the inner layer. The braided mesh comprisesinterwoven helical members, typically twelve, sixteen or twenty-fourinterwoven helical members, half extending in one direction and theother half extending in the in the counter direction. The tightness orbraid angle of the helical members to a line parallel with the axis ofthe catheter and intersecting the helical members is not critical, butis preferably about 45. The helical members are preferably made of aconductive material having a high modulus of elasticity. Preferredhelical members are made of stainless steel wire. Other methods forforming a braided mesh known in the art may be used. Finally the outerlayer is formed over the braided mesh by any suitable technique,preferably extrusion.

As would be recognized by one skilled in the art, the specific numberand composition of the layers of the tip section 14 is not critical. Forexample, the inner layer can be omitted, particularly if it is desiredto have a relatively small diameter tip section. The braided mesh canalso be omitted, in which case the tip section 14 can optionallycomprise a unitary core formed without additional plastic layers.Preferably whatever design is used, the tip section 14 is more flexiblethan the catheter body 12. The outer diameter of the tip section 14,like that of the catheter body 12, is preferably no greater than about 8french, more preferably about 6 French or less, but can vary dependingon the particular application for which the catheter is to be used.

In the depicted embodiment, the off-axis lumens 23, 24, 25 and 26 arearranged in diametrically opposed pairs. Each of the diametricallyopposed lumens 23 and 24 of the first pair carry an orientation sheath54, discussed further below. The diametrically opposed lumens 25 and 26of the second pair each carry a puller wire 32, also discussed furtherbelow. For reasons that will become apparent, the first pair of lumens23 and 24 is preferably generally perpendicular to the second pair oflumens 25 and 26. The precise size of the lumens is not critical andwill depend on the sizes of the components being carried by the lumens.As would be recognized by one skilled in the art, additional lumenscould be provided if desired. For example, a central lumen could beprovided for infusion of fluids.

A preferred means for attaching the catheter body 12 to the tip section14 is illustrated in FIG. 2. The proximal end of the tip section 14comprises an outer circumferential notch 34 that receives the innersurface of the outer wall 20 of the catheter body 12. The tip section 14and catheter body 12 are attached by glue or the like. Before the tipsection 14 and catheter body 12 are attached, however, the stiffeningtube 22 is inserted into the catheter body 12. The distal end of thestiffening tube 22 is fixedly attached near the distal end of thecatheter body 12 by forming a glue joint with polyurethane glue or thelike. Preferably a small distance, e.g., about 3 mm, is provided betweenthe distal end of the catheter body 12 and the distal end of thestiffening tube 22 to permit room for the catheter body 12 to receivethe notch 34 of the tip section 14. A force is applied to the proximalend of the stiffening tube 22, and, while the stiffening tube 22 isunder compression, a first glue joint (not shown) is made between thestiffening tube 22 and the outer wall 20 by a fast drying glue, e.g.Super Glue®. Thereafter a second glue joint is formed between theproximal ends of the stiffening tube 22 and outer wall 20 using a slowerdrying but stronger glue, e.g., polyurethane. Other suitable techniquesfor attaching the catheter body 12 and tip section 14 can also be usedin accordance with the present invention.

FIG. 4 provides a schematic side cross-sectional view of the tip section14. As shown in FIG. 4, the distal end of the tip section 14 carries atip electrode 38. Mounted along the length of the tip section 14 arethree ring electrodes 40. The length of each ring electrode 40 is notcritical, but preferably ranges from about 1 mm to about 3 mm. Thedistance between the ring electrodes 40 is not critical so long as theiredges do not touch. More or less ring electrodes 40 can be provided ifdesired.

The tip electrode 38 and ring electrode 40 are each connected to aseparate electrode lead wire 30. Each lead wire 30 extends through alumen 23 in the tip section 14, through the central lumen 18 in thecatheter body 12 and through the control handle 16. The proximal end ofeach lead wire 30 extends out the proximal end of the control handle 16and is connected to an appropriate connector, which can be plugged intoor otherwise connected to a suitable monitor, source of energy, etc.

The lead wires 30 are connected to the tip electrode 38 and ringelectrode 40 by any conventional technique. Connection of a lead wire 30to the tip electrode 38 is preferably accomplished by solder or thelike, as shown in FIG. 4. Connection of a lead wire 30 to a ringelectrode 40 is preferably accomplished by first making a small holethrough the wall of the tip section 14 into the lumen 23 through whichthe lead wire extends, as also shown in FIG. 4. Such a hole can becreated, for example, by inserting a needle through the wall of the tipsection 14 and heating the needle sufficiently to form a permanent hole.A lead wire 30 is then drawn through the hole by using a microhook orthe like. The end of the lead wire 30 is then stripped of any coatingand welded to the underside of the ring electrode 40, which is then slidinto position over the hole and fixed in place with polyurethane glue orthe like.

Two puller wires 32 extend through the catheter 10. Each puller wire 32extends from the control handle 16, through the central lumen 18 in thecatheter body 12 and into one of the off-axis lumens 25 and 26 of thetip section 14, as shown in FIG. 5. As described in more detail below,the proximal end of each puller wire 32 is anchored within the controlhandle 16, and the distal end of each puller wire 32 is anchored withinthe tip section 14.

Each puller wire 32 is made of any suitable metal, such as stainlesssteel or Nitinol. Preferably each puller wire 32 has a coating, such asa coating of Teflon® or the like. Each puller wire 32 has a diameterpreferably ranging from about 0.006 inch to about 0.0010 inch.Preferably both of the puller wires 32 have the same diameter.

Each puller wire 32 is anchored near the distal end of the tip section14. In the embodiment depicted in FIG. 5, the puller wires 32 are bothanchored in blind holes 37 in the tip electrode 38 by a welding or thelike. Alternatively, one or both puller wires 32 can be anchored to theside wall of the tip section 14, as described in U.S. patent applicationSer. No. 09/710,210, filed Nov. 10, 2000, the disclosure of which isincorporated herein by reference. Other means for anchoring the pullerwires 32 in the tip section 14 would be recognized by those skilled inthe art and are included within the scope of the invention.

In the depicted embodiment, the distal ends of the puller wires 32 areattached to opposite sides of the tip section 14. This design permitsdeflection of the tip section 14 in opposing directions.

The catheter 10 further comprises two compression coils 46, each insurrounding relation to a corresponding puller wire 32, as shown inFIGS. 2 and 3. Each compression coil 46 is made of any suitable metal,such as stainless steel. Each compression coil 46 is tightly wound onitself to provide flexibility, i.e., bending, but to resist compression.The inner diameter of each compression coil 46 is slightly larger thanthe diameter of its associated puller wire 32. For example, when apuller wire 32 has a diameter of about 0.007 inch, the correspondingcompression coil 46 preferably has an inner diameter of about 0.008inch. The coating on the puller wires 32 allows them to slide freelywithin the compression coil 46. The outer surface of each compressioncoil 46 is covered along most of its length by a flexible,non-conductive sheath 48 to prevent contact between the compression coil46 and the lead wires 30 within the central lumen 18. A non-conductivesheath 48 made of thin-walled polyimide tubing is presently preferred.

At the distal end of the catheter body, the two compression coils 46 arepositioned in diametric opposition within the stiffening tube 22 so thatthey can be aligned with the two off-axis lumens 25 and 26 in the tipsection 14 through which the puller wires 32 extend. The compressioncoils 46 and stiffening tube 22 are sized so that the compression coils46 fit closely and slidably within the stiffening tube 22. With thisdesign, the lead wires 30 distribute themselves around the twocompression coils 46 without misaligning the coils.

The compression coils 46 are secured within the catheter body 12 withpolyurethane glue or the like. Each compression coil 46 is anchored atits proximal end to the proximal end of the stiffening tube 22 in thecatheter body 12 by a glue joint (not shown). When a stiffening tube 22is not used, each compression coil is anchored directly to the outerwall 20 of the catheter body 12.

The distal end of each compression coil 46 is anchored to the distal endof the stiffening tube 22 in the catheter body 12 by a glue joint 52, ordirectly to the distal end of the outer wall 20 of the catheter body 12when no stiffening tube 22 is used. Alternatively, the distal ends ofthe compression coils 46 may extend into the off-axis lumens 26 and 28of the tip section 14 and are anchored at their distal ends to theproximal end of the tip section 14 by a glue joint. In the depictedembodiment, where the compression coils 46 are each surrounded by asheath 48, care should be taken to insure that the sheath is reliablyglued to the compression coil. The lead wires 30 can also be anchored inthe glue joint. However, if desired, tunnels in the form of plastictubing or the like can be provided around the lead wires at the gluejoint to permit the lead wires to be slidable within the glue joint.

The glue joints preferably comprise polyurethane glue or the like. Theglue may be applied by means of a syringe or the like through a holemade between the outer surface of the catheter body 20 and the centrallumen 18. Such a hole may be formed, for example, by a needle or thelike that punctures the outer wall 20 and the stiffening tube 22 that isheated sufficiently to form a permanent hole. The glue is thenintroduced through the hole to the outer surface of the compression coil46 and wicks around the outer circumference to form a glue joint aboutthe entire circumference of each sheath 48 surrounding each compressioncoil 46. Care must be taken to insure that glue does not wick over theend of the coil so that the puller wire cannot slide within the coil.

Within the off-axis lumens 25 and 26, each puller wire 32 is surroundedby a plastic sheath 42, preferably made of Teflon®. The plastic sheathes42 prevent the puller wires 32 from cutting into the wall of the tipsection 14 when the tip section is deflected. Each sheath 42 ends nearthe distal end of each puller wire 32. Alternatively, each puller wire32 can be surrounded by a compression coil where the turns are expandedlongitudinally, relative to the compression coils extending through thecatheter body, such that the surrounding compression coil is bothbendable and compressible.

Longitudinal movement of a puller wire 32 relative to the catheter body12, which results in deflection of the tip section 14 in the directionof the side of the tip section to which that puller wire is anchored, isaccomplished by suitable manipulation of the control handle 16. Asuitable bidirectional control handle for use in the present inventionis described in copending application Ser. No. 09/822,087, filed Mar.30, 2001 and entitled “Steerable Catheter with a Control Handle Having aPulley Mechanism”, the disclosure of which is incorporated herein byreference. Other suitable bidirectional control handles are described inU.S. Pat. Nos. 6,123,699, 6,171,277, 6,183,463, and 6,198,974, thedisclosures of which are incorporated herein by reference.

As illustrated in FIGS. 6 and 7, the tip section 14 includes a mechanismfor enhancing control over the deflection of the tip section. Themechanism comprises two orientation sheaths 54 that extend through thetwo lumens 23 and 24 of the first diametrically opposed pair in the tipsection 14. Each orientation sheath 54 comprises an elongated, veryflexible, thin walled polymer sheath, or tube. In a preferredembodiment, the two orientation sheaths 54 are formed of thin-walledpolyimide tubes which are on the order of 0.001 inches and which areinserted into the lumens and are then fed onto stainless steel mandrels.A Teflon heat shrink sleeve is then placed around the entire catheterbody and heat is applied to soften the orientation sheaths and the bodyof the catheter while the Teflon heat shrink sleeve squeezes thematerials together to bond the sheaths into the walls of the lumens.

The precise anchor point of the proximal end of each orientation sheath54 is not critical. Preferably the proximal ends of the sheaths 54 areanchored at approximately the same longitudinal position within thecatheter.

As noted above, the first pair of diametrically opposed lumens 23 and 24extend in a plane which is generally perpendicular to the plane of thesecond pair of diametrically opposed lumens 25 and 26. Accordingly, theorientation sheaths 54 are provided in the plane of deflection of thetip section 14. This arrangement improves the in-plane deflection of thetip section 14 because the orientation sheaths 54 reduce the tendency ofthe tip section to bend in a direction other than across the plane alongwhich the sheaths are positioned, i.e., the plane of deflection of thetip section. Such in-plane deflection increases the lateral tipstability which results in the user being able to create a greatercontact force against the heart tissue.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. Accordingly, the foregoing description should not beread as pertaining only to the precise structures described andillustrated in the accompanying drawings, but rather should be readconsistent with and as support to the following claims which are to havetheir fullest and fair scope.

1-6. (canceled)
 7. A steerable catheter comprising: an elongated,flexible tubular catheter body having proximal and distal ends and alumen extending therethrough; a tip section at the distal end of thecatheter body, the tip section comprising a flexible plastic tubinghaving first and second pairs of diametrically-opposed lumens extendingtherethrough, wherein the first pair of diametrically-opposed lumens isgenerally perpendicular to the second pair of diametrically-opposedlumens; a control handle at the proximal end of the catheter body; firstand second puller wires, each extending through one of the lumens of thefirst pair of diametrically-opposed lumens and through the lumen of thecatheter body, each having a proximal end anchored to the control handleand a distal end anchored to the tip section, whereby the first pullerwire is longitudinally moveable relative to the catheter body to causedeflection of the tip section in a plane in a first direction and thesecond puller wire is longitudinally moveable relative to the catheterbody to cause deflection of the tip section in a plane in a seconddirection opposite the first direction; and first and second tubularorientation sheath members each having proximal and distal ends, eachcomprised of a thin walled polymide tube, each extending through one ofthe lumens of the second pair of diametrically opposed lumens, eachhaving an outer diameter substantially the same as the inner diameter ofthe lumen through which it extends and wherein each tubular orientationsheath member is bonded along a substantial portion of the tubularorientation sheath member to the wall of one of the lumens.
 8. Asteerable catheter according to claim 1, wherein the tip section is moreflexible than the catheter body.
 9. A steerable catheter according toclaim 1, wherein each tubular orientation sheath member is fixedlyattached to the respective lumen of one of the second pair ofdiametrically opposed lumens near the distal end of the respectivelumen.
 10. A steerable catheter according to claim 5, wherein eachtubular orientation sheath member is bonded to the respective lumenalong the entire length of the tubular sheath.
 11. The steerablecatheter of claim 1 wherein the tubular sheath member has a wallthickness of approximately 0.001 inch.
 12. The steerable catheter ofclaim 1 wherein each tubular orientation sheath member is bonded to thelumen using heat.
 13. The steerable catheter of claim 1 wherein theproximal end of each tubular orientation sheath member is anchored atapproximately the same longitudinal position within the catheter.